As a material for switching elements for a power converter, silicon are widely used at present. However, the characteristics of switching elements made of silicon have almost reached their theoretical limits. As the materials that exceed the theoretical limit of silicon, there exist wideband gap semiconductors such as SiC (silicon carbide), GaN (gallium nitride) and diamond, the development of these being in progress. Power devices using wideband gap semiconductors have super low-loss and high-speed high-temperature operation characteristics. Of these wideband gap semiconductors, the most remarkable one is the SiC device, and SiC MOSFETs are regarded as promising switching for power converter.
In inverter circuits and the like that drive inductive loads, a diode is connected in parallel with a switching element. The diode of this kind is called a freewheeling diode, and functions to flow a reverse current. In an inverter using a SiC MOSFET as a switching element, a study on a configuration in which a SiC Schottky barrier diode (hereinafter SiC SBD) is connected in parallel with the SiC MOSFET, and the SiC SBD is used as a freewheeling diode, has been made.